A squid is a male or female that dates your friend. As a result you never see them again. The "squid" usually comes from a separate group of friends and takes that friend away to dark place.
Usually a squid is an overprotective boyfriend or clingy girlfriend.
It's based on a sailor being stolen from his ship by a giant squid and taken to the depth of the sea never to be seen again.

A male member of the U.S. Navy and is either found in a drunken or hungover state which is dependent on the number of hours the squid has been awake. Usually found in strip/go-go bars on the 1st and 15th of each month as those are paydays. Tends to drive a Mustang, however the squid generally does not have a license due to his number of DUI convictions.

Things squids like:
Weed. They are thought to be the only people on earth that can form an addition to the substance, which is quite the subject of many a discussion as the penalties of smoking week results in unemployment and imprisonment.

Hookers. Squids are known to fall in love with hookers and will often fight other squids to defend a hookers honor.

Jailor 1 - Hey wow this drunk tank sure is full today

Jailor 2 - Yeah those damn squids got paid today

.........
Commonwealth of Virginia - Sir you are being charges with DUI and we noticed in your passenger seat was a 17 year old girl that was drunk, high and naked.

A male who is a push-over when it comes to women. Most often, a squid encompasses certain characteristics that cause him to be an individual who frequently gets walked over by females. A squid is the type of guy who kisses a woman's ass and showers her with gifts with the intention of gaining her favor - it is the only way he knows how to gain a woman's attention because his game is extremely limited. However, despite his efforts, he never succeeds because of his pussified and chumpish squid-like manner.